This invention relates to a vehicle dynamic characteristic control apparatus and method for use with an automotive vehicle.
For example, Japanese Patent Kokai No. 61-67665 discloses a vehicle steering control apparatus for controlling a vehicle dynamic characteristic based upon various vehicle operating conditions. The apparatus includes a control unit for calculating a target yaw rate from a vehicle model specifying the target yaw rate as a function of vehicle speed and vehicle steering condition. The control unit controls the rear-wheel steering angle to achieve the target yaw rate.
It is proposed in Japanese Patent Kokai No. 61-113562 to provide accurate rear-wheel steering control by taking into account changes in the cornering powers of the rear and front road wheels in the presence of vehicle braking. The cornering powers of the rear and front wheels change upon application of braking to the vehicle although they are constant in the absence of vehicle braking.
The conventional steering control apparatus are satisfactory for providing good yaw rate characteristics in terms of yaw rate response (transient characteristic) and yaw rate gain (steady characteristic). However, they fail to provide good characteristics for another vehicle dynamic parameter. For example, the conventional steering control provides a feeling of discomfort since the transient and steady characteristics of the vehicle lateral speed are different in the presence of vehicle braking than in the absence of vehicle braking.